Active Denaturants for Biofuels to Improve Fuel Economy

ABSTRACT

Biofuels suitable for use in an internal combustion engine contain ethanol and are denatured with a performance-enhancing component. The performance-enhancing denaturant component includes an organic ingredient selected from the group consisting of friction modifiers, lubricity enhancers, anti-oxidants, and combinations thereof. An internal combustion engine fueled by such a biofuel has improved engine performance, including: increasing lubricant oil lubricity, reducing lubricant oil degradation, increasing engine component durability, and/or combinations thereof. In certain aspects, methods of increasing fuel economy are provided. The present disclosure also provides methods of formulating such biofuels.

FIELD

The present disclosure relates to biofuels containing ethanol and more particularly to denatured biofuels having active denaturants that provide superior performance benefits for internal combustion engines.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Due to increasing demand and diminishing supply of petroleum-based fossil fuels, various other sources for combustible fuel are being explored. Biofuels are derived from biological sources, some of which contain alcohol, in particular ethanol, which are suitable for use in internal combustion engines. Ethanol and substances which contain ethanol; however, are government regulated, including in the United States. In order to make ethanol unfit for beverage or internal human medicinal use, one or more additives, typically referred to as “denaturants,” are often mixed with ethanol. In certain countries like the United States, ethanol-containing substances, including ethanol fuels, are required to include at least one denaturant, typically present in the ethanol at about 0.5 to 5% by volume. Typical denaturant additives for ethanol include methanol, isopropyl alcohol, ethyl tertiary-butyl ether (ETBE), raffinate, naphtha, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, denatonium, natural gasoline, and/or unleaded gasoline. It would be desirable to develop biofuel compositions containing ethanol that are denatured and further provide enhanced performance benefits to internal combustion engines burning such biofuels.

SUMMARY

In various aspects, the present disclosure pertains to biofuels containing ethanol that are denatured with a performance-enhancing denaturant component. In certain aspects, the present disclosure provides methods of increasing fuel economy of an internal combustion engine consuming such a biofuel. In certain aspects, such a method comprises introducing a performance-enhancing denaturant with a biofuel comprising ethanol to form a fuel mixture for fueling the internal combustion engine. During operation of the engine, at least a portion of the performance-enhancing denaturant component present in the fuel mixture combines with an engine lubricant oil in the engine to improve engine performance. Such an improvement in engine performance and fuel economy relates to at least one of: increasing lubricant oil lubricity, reducing lubricant oil degradation, increasing engine component durability, or combinations thereof. In this manner, the performance-enhancing denaturant component increases fuel economy in comparison to a comparative biofuel including the ethanol, but lacking the performance-enhancing denaturant component. Additionally, in certain aspects, the presence of the performance-enhancing denaturant component in the fuel mixture with the biofuel improves engine oil life and increases oil drain intervals.

In yet other aspects, a biofuel composition is provided that comprises ethanol and at least one performance-enhancing denaturant component comprising at least one ingredient selected from the group consisting of friction modifiers, lubricity enhancers, anti-oxidants, and combinations thereof. In certain aspects, the biofuel composition is substantially free of conventional non-fuel denaturants for ethanol. In yet other aspects, the final biofuel composition, including the performance-enhancing denaturant component, optionally has an end boiling point of less than about 225° C. as determined by ASTM Test Method D86, for example.

In certain aspects, the present disclosure provides a method of formulating a biofuel for use in an internal combustion engine. The method comprises selecting a performance-enhancing denaturant component for a biofuel comprising ethanol, such that the final biofuel mixture has an end boiling point of less than about 225° C., as determined by ASTM Test Method D86, for example. The selection process includes comparing performance of an engine consuming a fuel mixture comprising the biofuel comprising ethanol and the performance-enhancing denaturant with the performance of the engine consuming a comparative biofuel comprising ethanol but lacking the performance-enhancing denaturant component. The performance enhancing denaturant component improves performance of the engine by one or more criteria selected from the group consisting of: increased fuel economy, increased engine oil lubricity, increased engine oil life, increased engine component durability, or combinations thereof. In certain aspects, the improved performance of the engine with the biofuel comprising ethanol and the performance-enhancing denaturant component results in greater than or equal to about 1% improvement in one or more of such criteria, optionally in certain aspects, greater than or equal to about 5% improvement in one or more of such criteria. In this manner, improved biofuel compositions can be formulated to provide significant engine performance advantages.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DETAILED DESCRIPTION

Bio-fuels are increasingly used for combustion in internal combustion engines. So-called “biofuel” generally refers to a class of fuels derived from biological sources, including plant and animal sources, including by way of example, biodiesel (which includes plant-based oil derivatives that are hydrolyzed to release glycerides, free fatty acids, or other substances, which are then converted to fatty acid esters useable as fuels, like mono-alkyl esters) and alcohol-based fuels. Alcohols, such as ethanol (C₂H₅OH), also known as ethyl alcohol or grain alcohol, can be produced from virtually any type of plant matter. In particular, grains like corn, barley, sorghum, and wheat, which contain high starch levels, can be broken down into sugars needed for traditional fermentation and conversion to ethanol or other alcohols, which is then used as a fuel. Other non-limiting examples of feedstock sources of alcohols for biofuels are cellulose-based and/or lignocellulose-based plant matter, like switch grass, corn stalks, wheat stalks, agricultural, municipal, paper industry, and forestry waste products.

The present teachings pertain to biofuels containing alcohol, specifically ethanol, which are used as fuels for internal combustion engines. While neat ethanol (100% ethanol content, also referred to in the United States as an “E100” fuel grade) can be used as a fuel for internal combustion engines, it is often blended with other traditional hydrocarbon fuels, like natural gasoline, unleaded gasoline, or diesel fuel. Such hydrocarbon-based fuels typically contain various organic compounds, including straight and branched chain paraffins, olefins, aromatics and naphthenic hydrocarbons, and other liquid hydrocarbonaceous materials suitable for spark ignition internal combustion engines. Since the heat of vaporization of ethanol is over two times that of gasoline, ethanol does not vaporize as readily at cold start-up temperatures prior to the engine reaching normal operating temperatures. To ensure proper cold-start behavior, the ethanol is often blended with hydrocarbons for colder climates.

Biofuels may contain various alcohols, including alkanols, having an alkane substituted with a hydroxyl group, such as methanol (CH₃OH), propanol (C₃H₇OH), butanol (C₄H₉OH), and the like. In certain non-limiting embodiments, the biofuels of the present disclosure optionally have an alcohol content ranging from greater than 0% by volume to about 99.5% by volume; optionally about 1% by volume to about 95% by volume; optionally about 3% by volume to about 95%; optionally about 5% by volume to about 90% by volume; optionally about 10% by volume to about 90% by volume.

Common ethanol-based fuel grade specifications include “E85,” which is an alternative motor fuel specified for use in the United States that comprises 85% by volume fuel grade ethanol and 15% by volume hydrocarbons in the gasoline boiling range (per the Energy Policy Act of 1992, Section 301(2)). Other common alternative motor fuel grades include by way of non-limiting example, E5 (about 5 volume % ethanol and 95% hydrocarbons in the gasoline boiling range), E7 (about 7 volume % ethanol and 93% hydrocarbons in the gasoline boiling range), E10 (about 10 volume % ethanol and 90% hydrocarbons in the gasoline boiling range), E60 (about 60 volume % ethanol and 40% hydrocarbons in the gasoline boiling range), and E95 (about 95 volume % ethanol and 5% hydrocarbons in the gasoline boiling range). Notably, the alcohol content in such fuel grades may vary significantly based on climate, season, and other similar considerations that impact fuel formulations.

In certain non-limiting examples, the biofuel has an ethanol alcohol content of less than or equal to about 25% by volume, optionally less than or equal to about 20% by volume, optionally less than or equal to about 15% by volume, optionally less than or equal to about 10% by volume. In yet other non-limiting examples, the biofuel optionally has an ethanol content of greater than or equal to about 60% by volume; optionally greater than or equal to about 65% by volume; optionally greater than or equal to about 70% by volume; optionally greater than or equal to about 75% by volume; optionally greater than or equal to about 80% by volume; optionally greater than or equal to about 85%; optionally greater than or equal to about 90%; optionally greater than or equal to about 95% alcohols by volume; and in certain aspects, optionally greater than or equal to about 97% ethanol by volume. Thus, in various aspects, the present disclosure contemplates use of the performance-enhancing denaturant component in a variety of ethanol-containing fuels having a wide range of ethanol contents.

Ethanol-based fuels are subject to various government regulations to prevent human consumption. In the United States, authorized denaturant additives for fuel alcohol (containing ethanol) include traditional fuel types of denaturants, including natural gasoline (mixtures of butane, pentane and hexane hydrocarbons extracted from natural gas), unleaded gasoline, raffinate, kerosene, deodorized kerosene, ethyl tert-butyl ether (ETBE), isopropyl alcohol, methanol, nitropropane, mixed isomers of heptane, and non-fuel denaturants, which are not typically considered as fuels for internal combustion engines (although may be capable of combustion), like, naphtha, toluene, rubber hydrocarbon solvent, methyl isobutyl ketone, denatonium benzoate, and combinations thereof. Such conventional denaturants are specified in 27 C.F.R. §19.10005, for example. While the amount of each denaturant present in the ethanol fuel varies, typical ranges are from about 2 to about 5% by volume to comply with certain regulations.

In accordance with the present teachings, methods are provided for replacing or supplementing conventional denaturants in ethanol-containing biofuels with one or more performance enhancing denaturants that improve the performance of an internal combustion engine that is fueled by the biofuel. In certain aspects, the biofuel is “substantially free” of conventional non-fuel denaturants, meaning that such conventional non-fuel denaturant compounds are present in the biofuel at less than about 1% by weight of the non-fuel conventional denaturant in the biofuel, more preferably less than about 0.5% by weight, optionally less than about 0.25% by weight, and in certain embodiments 0% of the non-fuel conventional denaturant is present in the biofuel. As noted above, non-fuel generally refers to denaturants that are not conventionally used as fuels for internal combustion engines, such as hydrocarbon-based fuels like gasoline.

Since ethanol has a lower energy content per volume than typical petroleum based gasoline or diesel fuels, it typically has lower miles per gallon fuel economy when it is used in internal combustion engines, which often requires engine adjustment. Further, the chemical properties of ethanol, which differ from those of gasoline or diesel, generally require certain modifications in engine design and control to maintain engine performance, emissions, fuel economy, and drivability. Biofuels containing ethanol, such as the E85 fuel blends, can be used in flex-fuel enabled internal combustion engine systems, generally referred to as flexible-fuel vehicles (FFV's).

Thus, in certain aspects, the present disclosure provides a method of increasing fuel economy of a biofuel for use in an internal combustion engine, by mixing a performance-enhancing denaturant component with the biofuel comprising ethanol to form a fuel mixture. This fuel mixture is then combusted in the internal combustion engine, where at least a portion of the performance-enhancing denaturant component combines with an engine lubricant oil in the engine during operation to improve engine performance by at least one of: increasing lubricant oil lubricity, reducing lubricant oil degradation, or combinations thereof, thereby increasing fuel economy in comparison to a comparative biofuel that lacks the performance-enhancing denaturant, but may instead contain a conventional denaturant. Additionally, in certain aspects, the presence of the performance-enhancing denaturant component in the fuel mixture with the biofuel improves engine oil life and increases oil drain intervals.

A “performance-enhancing denaturant component” is a material that is compatible with the biofuel, particularly ethanol, and provides one or more performance benefits to the internal combustion engine. In certain aspects, the performance-enhancing denaturant component is soluble and/or miscible in the ethanol-containing biofuel composition, including during transport and storage, by way of example. In certain aspects, the performance-enhancing denaturant component comprises at least one performance-enhancing ingredient and optionally comprises a plurality of performance-enhancing ingredients and/or other ingredients introduced to the biofuel as a denaturant component package. Thus, in certain aspects, the desired compatibility of the performance-enhancing denaturant component may be achieved by introduction of additional surface active agents, co-solvents, and/or compatibilizing agents to the denaturant component (in addition to the at least one performance-enhancing ingredient). In certain aspects, at least a portion of the performance-enhancing denaturant component is also soluble, miscible, or otherwise compatible with engine lubricant oil, as well, which may be provided by surface active, co-solvents or compatibilizing agents that associate with the performance-enhancing denaturant.

Further, in certain embodiments, the performance-enhancing denaturant component meets or enables the fuel mixture (to which it is added) to meet certain ethanol-fuel based performance specifications. In one embodiment, the fuel and/or denaturant component complies with one or more aspects of American Society of Testing and Materials (ASTM) Standard Specification D4806 for “Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-ignition Engine Fuel,” (December 2006), which is incorporated herein by reference in its entirety. In certain aspects, a performance-enhancing denaturant component meets ASTM D4806 Section 5.1, which specifies that a denaturant component, comprising one or more hydrocarbons, has an end boiling point of less than about 225° C. (about 437° F.), as determined by ASTM Test Method D86 “Test Method for Distillation of Petroleum Products at Atmospheric Pressure.” In yet other aspects, the final biofuel mixture composition, comprising the performance-enhancing denaturant component, has an end boiling point of less than about 225° C., as determined by ASTM Test Method D86 “Test Method for Distillation of Petroleum Products at Atmospheric Pressure.” ASTM D4806 Section 4.1 provides for denaturants being present in ethanol (prior to blending with other hydrocarbon-based fuels) at about 1.96 vol. % minimum and 5.0 vol. % maximum.

As noted above, by way of example, engine performance benefits include increased lubricant oil lubricity, reduced lubricant oil degradation and hence lengthened oil-life and/or increased engine oil change intervals, increased engine component durability, and increased fuel economy. In certain aspects, in contrast to many conventional fuel alcohol denaturants, the performance-enhancing denaturant component of the present disclosure is a surface active component (or group of surface active components) and thus, at least a portion of the performance-enhancing denaturant component is not completely consumed during combustion in the engine for its energy content.

Since in all engines, a certain amount of fuel gets introduced to the lubricant oil through the injection event and proceeds past the bore walls into the oil sump, fuel components can become diluted and mixed in with the engine oil. By way of example, approximately 97-99% of a fuel injected into a spark-ignition internal combustion engine may be combusted during the compression cycle, so that about 1-3% may remain after the combustion event. The present teachings use the introduction of fuel followed by combination with the engine lubricant oil within the engine to enhance engine performance and fuel economy. As the biofuel mixture combines with the lubricant oil, it is recirculated within the engine during operation, so that the combustible portion of the biofuel (e.g., the ethanol) is diluted in the oil and eventually re-consumed/re-combusted in subsequent events that may heat-up and re-vaporize the diluted oil/fuel mixture.

In accordance with the present teachings, a portion of the non-evaporative/non-combusted residual components of the biofuel, including a portion of the performance-enhancing denaturant component, will remain entrained in the lubricant oil. In accordance with the principles of the present disclosure, the biofuel contains a performance enhancing denaturant component, which comprises one or more performance enhancing ingredients, that provides continuous introduction and/or replenishing of active additive components to the lubricant engine oil delivered through the fuel, thus the engine lubricant oil is able to maintain its optimum properties to achieve the best fuel economy, lubrication, and/or durability.

Another benefit of the present teachings is that the rate of degradation of engine lubricant oil is reduced or minimized, so that engine performance is enhanced and oil replacement intervals (e.g., oil drain or change) can be lengthened and overall use of engine oil throughout the life of the engine is desirably reduced. In certain aspects, the use of such performance-enhancing denaturant additives in conjunction with ethanol-based biofuels will result in significantly reduced oxidation and degradation rates of the engine oil, as compared to regular conventional gasoline. In other words, the use of ethanol-based fuel in combination with such performance-enhancing denaturant additives will provide significant oil-life benefits. Additionally, the performance-enhancing denaturant additives will provide improved and more consistent lubrication properties of the engine oil, so that engine component durability is another added benefit.

In certain aspects, an improvement to fuel economy of a vehicle having an internal combustion engine fueled by the biofuel containing the performance-enhancing denaturant additive can be quantified, when such performance is compared to a comparative fuel economy of an engine burning a comparative biofuel, which is substantially the same as the inventive biofuel, but lacks the performance-enhancing denaturant component. The inventive biofuel compositions may also have improved fuel economy as compared to that of a vehicle fueled by a conventional gasoline or diesel fuel. In certain aspects of the present disclosure, a vehicle's fuel economy can be measured by normalizing the fuel consumption per unit distance while operating over a defined duty cycle such as the US Federal Test Procedure (US FTP) emissions cycle and/or the Highway Fuel Economy Test (HWFET), of which the respective relevant portions are incorporated by reference herein. Similarly, other suitable fuel economy tests include the standards in Europe referred to as the New European Drive Cycle (NEDC) and in Japan, referred to as the “Japan 10-15” cycle. These different fuel economy tests typically employ different cycles for testing (having different speed profiles, duration, acceleration/deceleration profiles, and frequencies of start/stops) and are well known in the art.

In certain embodiments, the performance-enhancing denaturant additive can increase fuel economy by greater than or equal to about 1%; optionally greater than or equal to about 2%; optionally greater than or equal to about 3%; optionally greater than or equal to about 4%; and in certain aspects, optionally greater than or equal to about 5%. In certain embodiments, the fuel economy may be improved by greater than or equal to about 10%; optionally greater than or equal to about 15%; optionally greater than or equal to about 20%; and in certain embodiments, may exceed about 25%.

By way of example, a fuel economy of a vehicle having an engine fueled by an inventive biofuel (e.g., an E85 fuel including a performance-enhancing denaturant component in accordance with the present teachings) is compared to a comparative fuel economy of the same vehicle run under the same conditions with E85 (lacking any performance-enhancing denaturant component, but having a conventional denaturant). In certain embodiments, fuel economy is improved by greater than or equal to about 1% for the inventive fuel mixtures (E85 and a performance-enhancing denaturant) as compared to the comparative fuel economy of the standard E85 fuel having a conventional denaturant. In yet other embodiments, such a fuel economy improvement is increased by greater than or equal to about 5%.

Likewise, in certain aspects, an engine fueled by a biofuel according to the present disclosure, including a performance-enhancing denaturant additive, has a quantifiable improvement in one or more of the following criteria as compared to an engine burning a comparative fuel, such as a biofuel comprising ethanol and lacking the performance-enhancing denaturant or a conventional gasoline fuel, for example. As noted above, fuel economy is optionally measured by the U.S. Federal Test Procedure (US FTP) emissions test and/or Highway Fuel Economy Test (HWFET); improved lubricant oil lubricity or reduction of friction of the engine oil lubricant, including both rotational and linear reciprocating friction modification, which can be measured by a number of lubrication industry wear tests, such as Pin and Vee Block, Pin-on-Disk, Four Ball, Block-on-Ring, High Frequency Reciprocating Rig (HFFR), and/or SRV Linear Oscillation; prevention of lubricant oil degradation as monitored by common lubricant industry tests, such as acid & base numbers, viscosity number and insolubles content; engine component durability as measured by common lubricant industry tests, such as the International Lubricant Standardization and Approval Committee (ILSAC) Sequence IVA and/or Sequence VIB engine performance tests; or combinations thereof. With improved engine oil lubricant performance over the operating life of the engine, better efficiency and cleaner combustion are achieved through less friction, less wear and tear between reciprocating components, and also tighter clearances to reduce undesirable oil leakage and seepage pathways.

In certain embodiments, the inventive biofuel having a performance-enhancing denaturant component improves one or more of these engine performance criteria (for an engine fueled by the inventive biofuel as compared to engine performance fueled by a comparative biofuel) by greater than or equal to about 1%; optionally greater than or equal to about 2%; optionally greater than or equal to about 3%; optionally greater than or equal to about 4%; and in certain aspects, greater than or equal to about 5%. In certain embodiments, one or more of such engine performance criteria may be improved by greater than or equal to about 10%; optionally greater than or equal to about 15%; optionally greater than or equal to about 20%; and in certain embodiments, may exceed 25%.

In certain aspects, the present disclosure provides a biofuel composition comprising ethanol and at least one performance-enhancing denaturant component selected from the group consisting of: friction modifiers, lubricity enhancers, antioxidants, and combinations thereof. It is understood that while general attributes of each of the above categories of active ingredients for the performance-enhancing denaturant component may differ, there may be some common attributes and any given ingredient may serve multiple purposes or fall within two or more of such categories of ingredients. In certain embodiments, the inventive biofuel may be a conventional biofuel comprising a conventional denaturant, as well as an additional performance-enhancing denaturant component. In other embodiments, the inventive biofuel composition is substantially free of conventional ethanol denaturants, particularly non-fuel conventional denaturants, as described previously above. In certain aspects, the biofuel composition further comprises a hydrocarbon-based fuel, like gasoline, diesel, and the like.

In certain aspects, compounds selected as performance-enhancing denaturant ingredients for use in the biofuels are miscible or soluble in the ethanol fraction (e.g., hydrophilic/oleophobic) and/or in the hydrocarbon fraction and lubricating oil (e.g., hydrophobic/oleophilic). The compounds may either be dispersible or soluble by themselves or by action of accompanying surface active agents, as previously described above. In certain aspects, these performance-enhancing denaturant component ingredients are oil compatible, meaning that the compound is soluble or dispersible in a lubricating oil composition or hydrocarbon fraction under normal blending or use conditions. In other aspects, performance-enhancing denaturant ingredients are ethanol-compatible, meaning that the compound is soluble or dispersible in ethanol or the biofuel under normal blending or use conditions.

In certain aspects, the performance-enhancing denaturant component of the biofuel composition comprises at least one organic compound, such as a hydrocarbon. In certain embodiments, at least one performance-enhancing ingredient is selected from the group consisting of: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof.

Depending upon the individual performance-enhancing denaturant component selected and the end use of the fuel, differing amounts of denaturant may be provided in the fuel composition. In certain aspects, as noted above, the performance-enhancing denaturant component will be included at a minimum amount that provides ethanol denaturing in accordance with applicable government regulations. In the United States, concentrations of denaturants in ethanol fuels are provided by 27 C.F.R §19.1005 and 27 C.F.R Part 21, among others, as well as denatured ethanol-fuel standard ASTM D4806. While not limiting, in certain embodiments, an ethanol-containing biofuel meets one or more aspects of current ASTM D4806 specifications, and contains denaturant component amounts of greater than or equal to about 2% by volume; optionally greater than or equal to about 3%; optionally greater than or equal to about 4% by volume; and in certain aspects, optionally greater than or equal to about 5% by volume.

In yet other aspects, a biofuel comprises a performance-enhancing denaturant component in an amount of greater than or equal to about 0.01% by weight; optionally greater than or equal to about 0.05% by weight; optionally greater than or equal to about 0.1% by weight; optionally greater than or equal to about 0.25% by weight; optionally greater than or equal to about 0.5% by weight; optionally greater than or equal to about 0.75% by weight; optionally greater than or equal to about 1% by weight; optionally greater than or equal to about 1.25% by weight; optionally greater than or equal to about 1.5% by weight; and in certain embodiments, optionally greater than or equal to about 1.75% by weight. In certain aspects, a biofuel composition comprising ethanol includes a performance-enhancing denaturant component has about 0.1 to about 1% weight; optionally about 0.2 to about 0.9% weight; and optionally about 0.25 to about 0.75% weight of the performance-enhancing denaturant component.

As discussed above, in certain aspects, the final biofuel composition mixture, containing a performance-enhancing denaturant component, has an end boiling point of less than about 225° C., which generally corresponds to a gasoline-based boiling range and can be measured by ASTM Test Method D86 “Test Method for Distillation of Petroleum Products at Atmospheric Pressure.” In yet other aspects, the performance-enhancing denaturant component itself has an average boiling point of less than about 225° C. As appreciated by those of skill in the art, where the performance-enhancing denaturant component includes a plurality of performance-enhancing ingredients or other components, like co-solvents, surface active agents, and compatibilizing agents, the total average boiling point of the component mixture as calculated by ASTM D86 is less than or equal to about 225° C. Thus, individual ingredients selected for the performance-enhancing denaturant component may individually have a boiling point of greater than 225° C., so long as when such ingredients are combined with other ingredients having lower boiling points, the total average boiling point is less than or equal to about 225° C. For example, where the performance-enhancing denaturant component comprises a mixture of three components A, B, and C, so that the respective mole fractions (x) in the performance-enhancing denaturant component are x_(A)+x_(B)+x_(C)=1, a bubble point/boiling point T_(BP) can be estimated by, P=x_(A)p*_(A)(T_(BP))+x_(B)p*_(B)(T_(BP))+x_(C)p*_(C)(T_(BP)), where p*_(i) is the vapor pressure of respective ingredient i (e.g., a, b, and c), P is the system pressure, and T_(BP) is the bubble point (boiling point) of the solution, where the performance-enhancing denaturant component is assumed to be an ideal liquid. The higher the vapor pressure of a liquid ingredient at a given temperature, the lower the normal boiling point (i.e., the boiling point at atmospheric pressure) of the liquid ingredient. In this manner, an ingredient having a lower vapor pressure p*_(i) and thus relatively high boiling point, which may exceed 225° C., may be used in the performance-enhancing denaturant component or fuel mixture in relatively small amounts to maintain an overall average boiling point of less than or equal to about 225° C.

Thus, suitable performance-enhancing ingredients for the performance-enhancing component include detergents, friction reducers, antioxidants, corrosion inhibitors, and/or anti-wear additives. As noted above, in various embodiments, such performance-enhancing ingredients are preferably organic hydrocarbon compounds, which are hydrocarbon based compounds (containing carbon and hydrogen) that may be substituted by oxygen, nitrogen and/or sulfur groups, by way of example. In various aspects, such performance-enhancing ingredients are non-metallic and ashless.

In certain embodiments, the performance-enhancing denaturant component comprises at least one of: a friction modifier, a lubricity enhancer, an anti-oxidant ingredient selected from the group of compounds consisting of: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof.

Anti-wear additives for internal combustion provide adequate anti-wear protection for the engine, by reducing friction and wear of metal parts. Many different types of anti-wear additives are known in the art. Suitable anti-wear ingredients esters of glycerol (propane-1,2,3-triol), including mono-oleates, di-oleates, and tri-oleates, mono-palmitates, and mono-myristates; alicyclics, amines, fatty alcohols, esters, diols, triols, fatty amides and the like. Such additives may be used in amounts ranging from about 0.01 to 6 weight %, preferably about 0.01 to about 4 weight % of the total fuel mixture.

Antioxidants retard the oxidative degradation of base oils of the engine lubricant during service. Degradation of lubricant oil can result in deposits on metal surfaces, development of sludge, or an increase in lubricant viscosity. A wide variety of antioxidants are known for use in lubricating oil compositions and are optionally suitable for use as a performance enhancing denaturant in the biofuel compositions of the present disclosure.

Suitable antioxidants include hindered phenols, typically including a sterically hindered hydroxyl group of a phenol, including derivatives of di-hydroxy aryl compounds in which the hydroxyl groups are in the ortho- or para-position to one another. Typical phenolic antioxidants include hindered phenols substituted with about C₆ or higher alkyl groups and alkylene coupled derivatives of such hindered phenols. Examples of phenolic materials of this type include 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful mono-phenolic antioxidants may include, for example, 2,6-di-alkyl-phenolic proprionic ester derivatives. Useful bis-phenolic antioxidants include: 2,2′-bis(6-t-butyl-4-heptyl phenol); 2,2′-bis(6-t-butyl-4-octyl phenol); 2,2′-bis(6-t-butyl-4-dodecyl phenol); 4,4′-bis(2,6-di-t-butyl phenol); and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Other antioxidants include aromatic amine antioxidants, including alkylated and non-alkylated aromatic amines, such as aromatic monoamines of the formula R₈R₉R₁₀N where R₈ is an aliphatic, aromatic or substituted aromatic group, R₉ is an aromatic or a substituted aromatic group, and R₁₀ is H, alkyl, aryl or R₁₁S(O)_(x)R₁₂ where R₁₁ is an alkylene, alkenylene, or aralkylene group, R₁₂ is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R₈ can be saturated and optionally has 1 to 20 carbon atoms, optionally about 6 to 12 carbon atoms. Both R₈ and R₉ can be aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R₈ and R₉ may be joined together with other groups such as sulfur (S).

Typical aromatic amines antioxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. The general amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthyl-amines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Polymeric amine antioxidants are also suitable. By way of example, aromatic amine antioxidants useful as a performance enhancing denaturant include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Other suitable antioxidants include sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof or peroxide-based antioxidants (e.g., low sulfur peroxide decomposers). Any of these antioxidants may be selected individually or in combination with one another for use as a performance enhancing denaturant. Such antioxidant additives may be used in amounts of about 0.01 to about 5 weight %, optionally about 0.01 to about 2 weight %, and in certain aspects, optionally about 0.01 to about 1 weight % of the total fuel mixture.

Friction modifiers that are suitable for use as a performance enhancing denaturant in the biofuel compositions of the present disclosure, include those materials that can alter the coefficient of friction of lubricant oil, and are also sometimes referred to as friction reducers or lubricity agents. In certain embodiments, suitable friction modifiers are organic friction modifiers including, for example, salts (ashless derivatives) of fatty acids, fatty alcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates, and comparable synthetic long-chain hydrocarbyl acids (e.g., oleic acid), alcohols, amides, esters, hydroxy carboxylates, and the like. In some instances fatty organic acids, fatty amines, and sulfurized fatty acids may be used as suitable friction modifiers. Ashless friction modifiers optionally include lubricant materials that contain effective amounts of polar groups, for example hydroxyl-containing hydrocarbyl base oils, glycerides, partial glycerides, glyceride derivatives, and the like. Polar groups in friction modifiers may include hydrocarbyl groups containing effective amounts of O, N, or S, individually or in combination.

Useful concentrations of friction modifiers may range from about 0.01 wt % to about 15 wt % or more, typically greater than or equal to about 0.1 wt % to less than or equal to about 5 wt % of the total fuel mixture. The performance enhancing denaturant ingredient can be selected to be a single friction modifier or combinations of friction modifiers, which can be mixed with alternate surface active materials.

The performance-enhancing denaturant component optionally includes co-solvents, compatibilizers, and/or detergents. As noted above, a material may have functionality or properties such that it is classified in one or more of the above categories, without limitation. A typical detergent is a surface-active agent having an anionic material that contains a long chain oleophilic/hydrophobic portion of the molecule and a smaller oleophobic portion of the molecule. The oleophobic/hydrophilic portion of the detergent is typically derived from an organic acid such as a sulfur acid, carboxylic acid, phenol, or mixtures thereof. Detergent ingredients suitable for the present fuel compositions are preferably non-metallic and ashless in nature. Examples of suitable detergent ingredients include those generally having (a) at least one hydrophobic hydrocarbon group; and (b) at least one polar group, such as a terminal group selected from (i) mono- or poly-amino groups having up to 6 nitrogen atoms; (ii) nitro groups and if required, nitro groups in combination with hydroxyl groups; (iii) hydroxyl groups combined with mono- or poly-amino groups; (iv) carboxyl groups or the alkali metal or alkaline earth metal salts thereof; (v) sulfonic groups; (vi) polyoxy-C₂-C₄-alkylene group with hydroxyl groups, mono- or poly-amino groups, or carbamate groups; (vii) carboxylic acid ester groups, (viii) groups with hydroxy and/or amino and/or amide and/or imide groups derived from succinic anhydride, and (ix) groups prepared by means of Mannich reaction of substituted phenols with aldehydes and mono- or poly-amines.

The hydrophobic hydrocarbon group (a) optionally has a number average molecular weight (M_(N)) of about 85 to about 5,000. Typical hydrophobic hydrocarbon groups, especially in combination with the polar groups (b)(i), (iii), (viii) or (ix), are the polypropenyl, polybutenyl and polyisobutenyl residues.

Examples of detergent ingredients containing mono- or poly-amino groups (b)(i) are polyalkene mono- or poly-amines based upon polypropene, polybutene, or polyisobutene having unsaturated bonds in terminal or central regions (e.g., in β or γ positions) of the molecule. For example, polyisobutene tends to be highly reactive and can be produced from polyisobutene which optionally contains up to 20% by weight of n-butene units by means of hydroformylation and reductive amination with ammonia, monoamines or polyamines, such as dimethylaminopropyl amine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. Suitable amine groups include polyalkyl amines having a nominal general formula of R²—NH₂ (II) where R² is a straight-chain or branched polyalkyl.

Other suitable ingredients containing mono-amino groups (b)(i) are hydrogenation products of the reaction products of polyisobutene with an average degree of polymerization (P) of 5 to 100 with nitric oxides (NO) or mixtures of nitric oxides and oxygen; or polyisobutenepoxide reacted with amine, followed by dehydrogenation and reduction of the amino alcohols.

Yet other examples of suitable detergent ingredients include those that contain nitro groups, and in certain aspects nitro groups combined with hydroxyl groups (b)(ii), which can optionally be reaction products of polyisobutenes with an average degree of polymerization (P) of 5 to 100 with nitric oxides or mixtures of nitric oxides and oxygen. These reaction products are typically mixtures of pure nitropolyisobutanes (e.g., α,β-dinitropolyisobutane) and mixed hydroxy nitropolyisobutanes (e.g., α-nitro-β-hydroxypolyisobutane).

Other suitable examples of detergents including a (b)(iii) group, which contains hydroxy groups in combination with mono- or polyamino groups, are the reaction products of polyisobutene epoxides and ammonia, mono- or polyamines.

Examples of detergent ingredients containing carboxyl groups (b)(iv) include polymers of C₂-C₄₀ olefins with maleic anhydride, optionally having a total molar mass of about 500 to about 20,000, where a portion of the carboxyl group(s) is reacted with alcohols or amines. Such additives are optionally used in combination with conventional fuel detergents, such as polyisobutenamines or polyetheramines.

In yet other aspects, the detergent ingredients optionally contain sulfonic groups (b)(v) and may be sulfosuccinic acid alkyl esters. Such additives are optionally used in combination with conventional fuel detergents, such as polyisobutenamines or polyetheramines.

Detergents optionally containing polyoxy-C₂-C₄-alkylene groups (b)(vi) are polyethers or polyetheramines, that can be formed by a reaction of C₂-C₆₀-alkanols, C₆-C₃₀-alkane diols, mono- or di-C₂-C₃₀-alkyl amines, C₁-C₃₀-alkyl cyclohexanols or C₁-C₃₀-alkyl phenols with 1 to 30 moles of ethylene oxide (EO) and/or propylene oxide (PO) and/or butylene oxide (BO) per hydroxy group or amino group. For certain polyetheramines, this reaction is followed by reductive amination with ammonia, monoamines or polyamines. Suitable polyethers, like tridecanol- or isotridecanol-butoxylates, isononylphenol butoxylates, polyisobutenol butoxylates, and propoxylates can also be further reacted with ammonia.

Detergents including carboxylic acid ester groups (b)(vii) are optionally selected from esters of mono-, di- or tricarboxylic acids with long-chain alkanols (e.g., C₆-C₂₄) or polyols. Aliphatic or aromatic acids may be used as mono-, di- or tricarboxylic acids and suitable ester alcohols and polyols are in particular long-chain molecules with C₆-C₂₄, for example. Suitable esters are the adipates, phthalates, isophthalates, terephthalates and trimellitates of isooctanol, isononanol, isodecanol and isotridecanol.

Suitable non-limiting examples of detergents including (b)(viii) groups (derived from succinic anhydride with hydroxy and/or amino and/or amido and/or imido groups) include corresponding derivatives of polyisobutenyl succinic anhydride, which are obtainable by reacting conventional or highly reactive polyisobutene with maleic acid anhydride, either thermally or via chlorinated polyisobutene. In this regard, derivatives with aliphatic polyamines are suitable including ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine.

Lastly, suitable detergent ingredients including (b)(ix) groups, produced by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines, are optionally reaction products of polyisobutene-substituted phenols with formaldehyde and mono- or polyamines, like ethylene diamine, diethylene triamine, triethylene tetraamine, tetraethylene pentamine or dimethylaminopropyl amine.

One or more co-solvents for the performance-enhancing denaturant component optionally include those selected from the group consisting of C₂ to C₁₂ aliphatic alcohols, C₃ to C₁₂ ketones, C₂ to C₁₂ ethers, esters, oxides, phenols, and the like. A plurality of co-solvents can be employed, including mixed alcohols, ethers, esters, oxides, phenols and/or ketones.

Suitable compatibilizing agents for use in the performance-enhancing component include organic compounds having an intermediate solubility parameter (δ), based on cohesive energy density (as an approximation of polarity of the compound), and moderate to strong hydrogen-bonding capacity. In certain aspects, compatibilizing agents optionally have a solubility parameter of about 7 to about 14 and moderate to strong hydrogen-bonding capacity. Suitable classes of such organic solvents are alcohols, ketones, esters, and ethers.

In certain aspects, the biofuel can also include supplemental conventional additives known in the art (in addition to performance-enhancing denaturant components), for example, non-metallic dispersants, non-metallic detergents, corrosion and rust inhibitors, metal deactivators, chromophoric agents, defoamants, dyes, markers, biocides, antistatic additives, antiknock additives, octane enhancers, combustion enhancers, and combinations thereof, by way of non-limiting example.

In certain aspects, the present disclosure provides methods of producing a denatured biofuel composition that has beneficial fuel economy, such as those previously described above. For example, in certain aspects, the method includes introducing a performance-enhancing denaturant component to a biofuel comprising ethanol. The performance-enhancing denaturant component can be introduced to the ethanol-based biofuel at the site of biofuel production or processing (e.g., at the biofuel production site/plant) to produce a precursor to a fuel mixture. Where substantially all of the biofuel is ethanol (e.g., 97-100% ethanol), introducing the performance-enhancing denaturant component in such a manner suitably denatures the ethanol product for additional transport and processing. The performance-enhancing denaturant component is combined with the ethanol to provide advantageous denaturing and thus, substitutes for conventional denaturants so that the use of such conventional denaturants is no longer required. The denatured biofuel composition can then be transported and stored, prior to further processing to optionally introduce other fuel-based additives or hydrocarbon and/or petroleum based fuels for a fuel mixture. In yet other embodiments, the performance-enhancing denaturant component is optionally added to a biofuel comprising ethanol concurrently or around the same time (for example, in the same facility) as other additives and/or fuels that form a fuel mixture. Optionally, such a biofuel may already contain a conventional denaturant and thus may further include the performance-enhancing denaturant component. In certain embodiments, the biofuel composition is substantially free of conventional non-fuel denaturants.

In certain aspects, the present disclosure provides a method of formulating a biofuel for use in an internal combustion engine. First, a performance-enhancing denaturant component for a biofuel comprising ethanol is selected. The selection process enables biofuel formulation with performance enhancing denaturant components having particularly advantageous benefits for use in an internal combustion engine. An engine's performance is compared when consuming the inventive biofuel having the performance-enhancing denaturant and when consuming a comparative biofuel, having the same or similar composition as the inventive biofuel, but lacking the performance-enhancing denaturant. For example, in certain aspects, the comparative biofuel composition may have one or more conventional denaturants in lieu of the performance-enhancing denaturant component. Ideally, the engine's performance is measured by operating the engine under the same conditions during testing. By way of example, an engine's performance can be tested via conventional dynamometer testing and/or vehicle testing known in the art. Comparative testing may also include those tests described above, including tests for fuel economy (e.g., U.S. Federal Test Procedure (US FTP) emissions test and/or Highway Fuel Economy Test (HWFET)); lubricant oil lubricity or friction reduction tests (e.g., rotational and/or linear reciprocating friction modification wear tests, such as Pin and Vee Block, Pin-on-Disk, Four Ball, Block-on-Ring, High Frequency Reciprocating Rig (HFFR), and/or SRV Linear Oscillation); lubricant oil degradation (e.g., testing of acid & base numbers of engine oil lubricant, engine oil viscosity number and engine oil insolubles content); engine component durability (e.g., International Lubricant Standardization and Approval Committee (ILSAC) Sequence IVA and/or Sequence VIB engine performance tests); or combinations of any of these or similar tests. With improved engine oil lubricant performance over the operating life of the engine, better efficiency and cleaner combustion are achieved through less friction, and wear and tear, between reciprocating components, and also tighter clearances to reduce undesirable oil leakage and seepage pathways.

An inventive biofuel comprising a performance-enhancing denaturant component, for example having greater than 0 and less than or equal to about 5 weight % of the performance-enhancing denaturant component can be compared to a comparative conventional biofuel comprising E100 denatured with conventional straight gasoline at greater than 0 and less than about 15 weight %, by way of non-limiting example. Testing provides fuel economy effects on engine performance of the inventive biofuel and comparative biofuel compositions at different oil life intervals. The improved performance of the engine results in a greater than or equal to about 1% improvement; ideally greater than or equal to about 5% improvement, and in certain aspects, greater than or equal to about 10% improvement in said one or more criteria selected from the group consisting of: increased fuel economy, increased engine oil lubricity, increased engine oil life, engine component durability, or combinations thereof.

In certain aspects, the selection of the performance-enhancing denaturant includes selecting at least one ingredient from the group consisting of: a friction modifier, a lubricity enhancer, an anti-oxidant, and combinations thereof. In certain aspects, such an ingredient is a friction modifier, lubricity enhancer, and/or anti-oxidant described above, including those selected from: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof. 

1. A method of increasing fuel economy of an internal combustion engine consuming a biofuel, the method comprising: introducing a performance-enhancing denaturant component to a biofuel comprising ethanol to form a fuel mixture for fueling the internal combustion engine, wherein at least a portion of the performance-enhancing denaturant component combines with an engine lubricant oil in the engine during operation to improve engine performance by at least one of: increasing lubricant oil lubricity, reducing lubricant oil degradation, increasing engine component durability, or combinations thereof, thereby increasing fuel economy in comparison to the engine being fueled by a comparative fuel lacking the performance-enhancing denaturant component.
 2. The method of claim 1, wherein the increase in fuel economy is greater than or equal to about 1%.
 3. The method of claim 1, wherein the increase in fuel economy is greater than or equal to about 5%.
 4. The method of claim 1, wherein said fuel mixture comprises about 5 volume % to about 95 volume % of ethanol.
 5. The method of claim 1, wherein after said introducing, a hydrocarbon-based fuel is subsequently introduced to said fuel mixture.
 6. The method of claim 1, wherein said performance-enhancing denaturant component comprises at least one organic ingredient selected from the group consisting of: friction modifiers, lubricity enhancers, anti-oxidants, and combinations thereof.
 7. The method of claim 6, wherein said performance-enhancing denaturant component further comprises at least one additional ingredient selected from the group consisting of: surface-active agents, detergents, co-solvents, compatibilizing agents, and combinations thereof.
 8. The method of claim 6, wherein said at least one ingredient is selected from the group consisting of: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof.
 9. The method of claim 6, wherein a final biofuel composition comprising said ethanol and said performance-enhancing denaturant component has an end boiling point of less than about 225° C.
 10. A biofuel composition comprising: ethanol and a performance-enhancing denaturant component comprising at least one organic ingredient selected from the group consisting of: friction modifiers, lubricity enhancers, anti-oxidants, and combinations thereof.
 11. The biofuel composition of claim 10, wherein the biofuel composition is substantially free of conventional non-fuel denaturants.
 12. The biofuel composition of claim 10, wherein the biofuel composition comprises about 5 volume % to about 95 volume % of ethanol.
 13. The biofuel composition of claim 12, wherein the biofuel composition further comprises a hydrocarbon-based fuel.
 14. The biofuel composition of claim 10, wherein said at least one organic ingredient is selected from the group consisting of: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof.
 15. A method of formulating a biofuel for use in an internal combustion engine, the method comprising: selecting a performance-enhancing denaturant component for a biofuel comprising ethanol so that a final biofuel mixture comprising ethanol and said performance-enhancing denaturant component has an end boiling point of less than about 225° C., by comparing performance of the engine consuming said final biofuel mixture with the engine consuming a comparative biofuel comprising said ethanol but lacking said performance-enhancing denaturant component, wherein the performance enhancing denaturant component contributes to improved performance of the engine by one or more criteria selected from the group consisting of: increased fuel economy, increased engine oil lubricity, increased engine oil life, increased engine component durability, or combinations thereof.
 16. The method of claim 15, wherein the improved performance of the engine results in greater than or equal to about 1% improvement in said one or more criteria selected from the group consisting of: increased fuel economy, increased engine oil lubricity, increased engine oil life, increased engine component durability, or combinations thereof.
 17. The method of claim 15, wherein the improved performance of the engine results in greater than or equal to about 5% improvement in said one or more criteria selected from the group consisting of: increased fuel economy, increased engine oil lubricity, increased engine oil life, increased engine component durability, or combinations thereof.
 18. The method of claim 15, wherein said selecting of said non-fuel performance-enhancing denaturant comprises selecting at least one organic ingredient from the group consisting of a friction modifier, a lubricity enhancer, an anti-oxidant, and combinations thereof.
 19. The method of claim 18, wherein said performance-enhancing denaturant component further comprises at least one additional ingredient selected from the group consisting of: surface-active agents, detergents, co-solvents, compatibilizing agents, and combinations thereof.
 20. The method of claim 18, wherein said at least one organic ingredient is selected from the group consisting of: carboxylic acids, di-acids, esters, and derivatives thereof; amines, amides, imides, and derivatives thereof; hindered phenols and derivatives thereof; aromatic and aryl amines and derivatives thereof; and combinations thereof. 